准噶尔盆地北三台凸起西斜坡白垩系高频层序地层与油气成藏模式

基于Vail经典层序地层学理论,运用岩芯、测井及地震资料,采用井震对比综合分析方法,建立了准噶尔盆地北三台凸起西斜坡白垩系层序地层格架,针对主要含油气体系域展开了高频层序划分,综合研究了含油气准层序的构造特征和成藏模式,并总结成藏特点,为白垩系隐蔽油气藏的勘探指明方向。结果表明:北三台凸起西斜坡白垩系可以划分为4个三级层序和6个体系域,油气显示主要分布在SQ2的低位体系域和水进体系域中,可将其划分为4个准层序组和14个准层序,并通过油气显示归位确定其中3个准层序为白垩系的含油气高频层序地层单元;白垩系底部3个含油气地层单元均为超覆尖灭,其构造形态可划分为沙南鼻突、西泉鼻突和北38鼻突;典型出油点主要形成了西泉鼻突成藏模式和北38鼻突成藏模式,前者为斜坡背景下岩性尖灭控藏,后者为构造与地层沉积尖灭复合控藏;白垩系成藏具有受鼻突构造、局部断裂、地层超覆尖灭线以及岩性突变带控制的特点。总之,准噶尔盆地北三台凸起西斜坡白垩系下一步勘探应以西泉鼻突与北38鼻突的地层超覆尖灭线附近发育的地层圈闭为主。

High-frequency Sequence Stratigraphy and Hydrocarbon Accumulation Model of Cretaceous in Western Slope of Beisantai Uplift,Junggar Basin

Based on Vail classic sequence stratigraphy theory,according to the core,well logging and seismic data,the sequence stratigraphic framework of Cretaceous in western slope of Beisantai Uplift,Junggar Basin was established by the well-seismic correlation comprehensive analysis method;high-frequency sequences for the main system tracts with hydrocarbon were divided;the structural characteristics and hydrocarbon accumulation models of parasequences with hydrocarbon were comprehensively studied,and the accumulation characters were summarized;the direction for exploration of subtle reservoirs of Cretaceous was shown.The results showed that Cretaceous in western slope of Beisantai Uplift could be divided into four third-order sequences and six system tracts;hydrocarbon showing mainly distributed in low system tract and transgressive system tract of SQ2,which could be divided into four parasequence sets and fourteen parasequences,and three of the parasequences were high-frequency sequence stratigraphic units of Cretaceous with hydrocarbon through hydrocarbon homing;three stratigraphic units with hydrocarbon at the bottom of Cretaceous were overlap and pinchout,and the structural configuration could be divided into Shanan,Xiquan and Bei38 nasal processes;there were Xiquan and Bei38 nasal process accumulation models in the typical oil points,the former was controlled by lithologic pinchout in the slope,and the latter was controlled by complex structural and stratigraphic lapouts;Cretaceous accumulation was controlled by nasal structure,partial fracture,stratigraphic overlap pinchout line and lithologic break zone.In general,the next exploration target of Cretaceous in westen slope of Beisantai Uplift,Junggar Basin should be mainly stratigraphic trap near the stratigraphic overlap pinchout lines of Xiquan and Bei38 nassal processes.